Abstract: 316L austenitic stainless steel has a strong strain hardening character. It can accurately predict the welding residual stresses to select a suitable hardening model. In this study,a new nonlinear mixed hardening model was developed. An uncoupled 3D thermal and mechanical analysis was carried out by using the software code SYSWELD to simulate the welding residual stress in a 3-pass slot weld. The results show that material hardening model has an important influence on the predicted residual stress. The effect of hardening model is more obvious with the increase of thermal cycles. Compared with the measured residual stress,kinematic hardening model underestimates the welding residual stress,and isotropic hardening model overestimates the residual stress. An excellent agreement with the measured data can be obtained to use nonlinear mixed hardening model to simulate the welding residual stresses.